LTM4650 datasheet(72/138 Pages) AD

72 / 138 page

LTM4664A

Rev. 0

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it is driven quickly. If the ratio of CLOAD to COUT is greater

than 1:50, the switch rise time should be controlled so that

the load rise time is limited to approximately 25 • CLOAD.

Thus a 10µF capacitor would require a 250µs rise time,

limiting the charging current to about 200mA.

PolyPhase® Configuration

When configuring a PolyPhase rail with multiple

LTM4664As, the user must share the SYNC, COMP_na,

COMP_nb SHARE_CLK, FAULT_Cn, and ALERT pins of

these parts. Be sure to use pull-up resistors on FAULT_

Cn, SHARE_CLK and ALERT. One of the part’s SYNC pins

must be set to the desired switching frequency, and all

other FREQUENCY_SWITCH commands must be set to

External Clock. If an external oscillator is provided, set

the FREQUENCY_SWITCH command to External Clock for

all parts. The relative phasing of all the channels should

be spaced equally. The MFR_RAIL_ ADDRESS of all the

devices should be set to the same value.

Multiple channels need to tie all the VOSNS+ pins together,

and all the VOSNS– pins together COMP_na and COMP_

nb pins together as well. Do not assert bit[4] of MFR_

CONFIG_ALL except in a PolyPhase application. See

application example Figure 50.

CONNECTING THE USB TO I2C/SMBUS/PMBUS

CONTROLLER TO THE LTM4664A IN-SYSTEM

The LTC USB-to-I2C/SMBus/PMBus adapter (DC1613A

or equivalent) can be interfaced to the LTM4664A PSM

on the user’s board for programming, telemetry and sys-

tem debug. The adapter, when used in conjunction with

LTpowerPlay, provides a powerful way to debug an entire

power system. Faults are quickly diagnosed using telem-

etry, fault status commands and the fault log. The final

configuration can be quickly developed and stored to the

LTM4664A PSM EEPROM. Figure 34 illustrates the appli-

cation schematic for powering, programming and com-

munication with one or more LTM4664As PSM via the

LTC I2C/SMBus/PMBus adapter regardless of whether or

not system power is present. If system power is not pres-

ent, the dongle will power the LTM4664A PSM through

the VDD33 supply pin. To initialize the part when VIN is not

applied and the VDD33 pin is powered, use global address

0x5B command 0xBD data 0x2B followed by address 0x5B

command 0xBD data 0xC4.The LTM4664A PSM can now

communicate with, and the project file Figure 34. Controller

Connection can be updated. To write the updated project file

to the NVM issue a STORE_USER _ALL command. When

VIN is applied, a MFR_RESET must be issued to allow the

PWM POWER to be enabled and valid ADCs to be read.

VIN

VDD33

VDD25

SDA

1µF

VGS MAX ON THE TP0101K IS 8V IF VIN > 16V

CHANGE THE RESISTOR DIVIDER ON THE PFET GATE

1µF

4664A F34

10k

100k

TP0101K

ISOLATED

3.3V

SDA

SCL

TP0101K

100k

LTC

CONTROLLER

HEADER

TO LTC DC1613

USB TO I2C/SMBus/PMBus

CONTROLLER

SCL

WP PGND/SGND

LTM4664A PSM

VIN

VDD33

SDA

SCL

WP PGND/SGND

LTM4664A PSM

10k

VDD25

Figure 34. Controller Connection

DUAL 25A/30A PSM APPLICATIONS INFORMATION

LTM4650 Datasheet(PDF) 72 Page - Analog Devices

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